1. Technical Field
The present invention pertains generally to the field of hauling cargo on highways with motor vehicles and more specifically to cargo carried with trailers.
2. Description of Related Art
A loaded cargo is usually carried over a hauling cargo bed which is mounted on a truck chassis frame. In order to achieve this, it is required to lift up the cargo onto the hauling bed. Many designs have sought to ease this task. U.S. Pat. No. 2,485,300 issued to Lisota uses a tilting and moving bed to load or unload a truck. Many refinements of this method are used to lift up large cargo containers on truck chassis. LaMora in U.S. Pat. No. 5,460,473 shows a system using a trailer to haul two containers in line. Alternately, U.S. Pat. No. 6,099,232 to Dixon shows a smaller cargo bed loaded into a pick up truck. Although these methods are widely used today, they are not practical for unpacked cargoes, nor can they be used to load or unload live animals.
U.S. Pat. No. 2,230,014 issued to Haven describes a lifting/lowering trailer using a system of cams and links. Verschage in U.S. Pat. No. 4,372,572 uses cams, links and hydraulic cylinders to lift heavy loads, such as fork lifts. U.S. Pat. No. 5,630,693 issued to Sobina shows a design of a level lift trailer bed which is kept in alignment by inner sliding telescoping guides as it is lifted by hydraulic cylinders at each corner of the chassis. In each of these devices, the cargo or load carrying member is a permanent integral part of the trailer.
Adding versatility to his tilting frame trailer, Pihlstrom in U.S. Pat. No. 4,930,799 is able to interchange the cargo carrier. But, this system can not lift a loaded cargo carrier.
Therefore, there is a strong desire for a simple, reliable and heavy capacity level lifting trailer system capable of detaching from its cargo bed, or from an interchangeable bed, in some other configurations.